At a Glance

• Physics

Instructional Level

• College & CEGEP

• Mechanics

Social Plane(s)

• Group
• Whole Class

• Collecting & seeking information
• Discussing
• Solving problems
• Analyzing

Technical Details

Useful Technologies

• Computers or interactive whiteboards
• Tracker software
• Excel
• Video with phone
• A bottle rocket

Class size

• Small (20-49)

Time

Single class period (< 90 mins)

Instructional Purpose

• Exploration & inquiry

• Array
• Array

Overview

In this activity, students will be using the Tracker software to analyze the equations of motion of a bottle rocke.

In groups of 3-4, students go outdoors to record a video of a bottle rocket being launched. This is done as a class, however each group will take their own videos. Students should ensure that a distance calibration tool is visible in the video, that the camera is stationary throughout the duration, and that they are far enough back from the bottle rocket that the angular geometry does not interfere significantly with their results. Students should ensure that at least ...

In this activity, students will be using the Tracker software to analyze the equations of motion of a bottle rocke.

In groups of 3-4, students go outdoors to record a video of a bottle rocket being launched. This is done as a class, however each group will take their own videos. Students should ensure that a distance calibration tool is visible in the video, that the camera is stationary throughout the duration, and that they are far enough back from the bottle rocket that the angular geometry does not interfere significantly with their results. Students should ensure that at least one member of their group is filming using their phone.

Students then return to a computer and upload the video into the Tracker software (for example by emailing themselves the video), and calibrate the axes and distances. They then track the bottle rocket using auto-tracking function of the software (or manually if needed), which produces tabulated data for the position as a function of time.

Students import the data into a spreadsheet program such as Excel. They plot the position as a function of time, then divide the motion into four different stages:

a) Propulsion phase (accelerating upward)
b) Drag (the rocket has a high velocity and drag forces are large)
c) Projectile motion (constant acceleration due to gravity)
d) Terminal velocity.

Students analyze each stage and fit equations of motion to the data. More advanced students can make use of their calculus knowledge to fit first to 2nd order polynomials, then add higher orders.

Students can then see that during certain phases the acceleration was not constant, as it is fit by a higher order polynomial. They discuss the meaning of this and the reasons why the acceleration may not be constant (for example, changing mass and pressure, changing drag forces).

Instructional Objectives

Students learn to analyze and fit equations of motion to raw data.

Students learn how to break motion into different regimes based on what forces dominate at any given time.

Contributor's Notes

Kevin Lenton

Vanier College, Montreal, QC

Benefits

Students can apply their knowledge of calculus to the physics problem, clearly identifying the relationship between whether or not acceleration is constant and the order of the polynomial fitting the equation of motion.

Students learn to analyze and plot data and learn to work with spreadsheets, including using formulas and plotting.

Students take something out in the real world and analyze it in the physics classroom. Despite this, the activity hits many important learning objectives. By using their own phones to film this, the activity becomes more personally relevant for students.

Challenges

As students are using real world data, it can get messy. The deviation from ideals can confuse students.

The bottle rocket is not always very reliable, it’s a good idea to have a prepared video (for example from Youtube) in case the demonstration fails. The bottle rocket also moves very fast, and can be difficult for students to track.

One challenge to this activity is that it has dependencies on several technologies, and it is therefore important to test everything beforehand. You should test your workstations, making sure you can take a video with your phone and get it onto the stations where students are working, then upload it into the motion tracker.

Tips

This activity can be paired with the other Tracker activities to promote continuity and familiarize students with the software. Specifically, this activity is designed to be completed after the Falling Object Tracker activity.

This activity should be done relatively late in the semester to ensure students gain the full benefits of their knowledge of calculus, and see the meaning of higher order polynomials as non-constant accelerations.

Brightly coloured tape around the rocket helps the tracker pick it up.